¹KFKI Atomic Energy Research Inst., Radiation and Environmental Physics Dept.
²National Inst. For Radiobiology and Radiohygiene, Division of Cellbiology
³National Inst. For Radiobiology and Radiohygiene, Division of Molecular and Tumorbiology
⁴Simon Bolivar University, Radiopharmacy Laboratory, Caracas, Venezuela
⁵National Institute for Oncology

Introduction

During the last two years the Biological Irradiation Facility was further improved in order to enlarge the activity on the field of radiation biology:

• the irradiation cavity was modified to avoid the mechanical shock of the experimental animals and to decrease the total irradiation time for a given dose without changing the quality of the radiation;
• also the control system was upgraded to be able to measure low neutron dose with higher accuracy;
• a new set of external filters were manufactured to produce softer neutron spectra for BNCT and to increase the neutron-to-gamma dose ratio up to ∼70 in order to study the biological effects of low neutron dose only, without significant gamma contamination: it was also our aim to construct such spectra which can be considered as so called “realistic neutron spectra”, may be found in work places, to be used for dosimetry purposes.

For illustration, in Fig. 8 two filtered, “realistic spectra” are presented, used for testing the averaged responses of semiconductor detectors under development for personal dosimetry and for low dose experiments.

1. Lead 200, Al 93, Fe 20, Pb 63, H₂O 480 mm,
2. Bismuth 200, Al 85, Fe 30, Pb 63, H₂O 480 mm.